I agree with Claes. I believe if you look in the Ebay stores there is a seller offering these for sale. I am at work and don't have my book, but I believe the originals are even larger than you say, and yes, made of tin. I think the circle itself is 10" round, then the rectangle top is like 4" or so in height for a total of 14" or more tall. I'm obviously no expert, but when you can find an item in Ebay stores and in a material it was never offered in originally, I stay away from them! I also think all the originals are AM41 dated at the bottom. I hope you are able to return the item. Good luck!
Always looking for Mobil items I don't already have!